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Fig. 3 Muscle biopsy images from our patients all homozygous for p.G25Rfs*74. (A) Muscle biopsy (quadriceps) from a patient in Family 2 (performed at age 41 years). Images show marked fibre hypertrophy and increased fibrosis with endo and perimysial fatty infiltration. Labelling for collagen VI appears normal. (B) Muscle biopsy (right quadriceps) from a Family 4 patient (aged 6 years). Biopsy shows predominantly neuropathic aspects with neurogenic atrophy (arrow) and thickening of the endomysium and perimysium. Fascicular grouping of type 1 fibres implicates a chronic neurogenic process. NADH-TR shows the presence of moth-eaten fibres (non-specific finding). (C) Muscle biopsy (quadriceps) from a patient from Family 5 (aged 41 years). Marked variation in fibres size and increased endomysial fibrosis with mostly perimysial fatty infiltration. Rimmed vacuoles are shown with an arrow. There is a large predominance of type 2 fibres. Labelling for collagen VI appears normal. (D) Muscle biopsy from the index case in Family 12 (right vastus lateralis, age 52). Myopathic features are present, with marked fibre lobulation and variable degree of whorling of myofibrils (arrow). Endomysial fatty infiltration. Large areas of fibre grouping in this biopsy as well indicates a neurogenic aetiology. ATPase staining was performed at pH 4.2. H&E = haematoxylin and eosin.